This invention relates to apparatus for fabricating wood structures, and is more particularly concerned with apparatus for fabricating relatively shallow-depth (e.g., 12 to 36 inches) flat trusses used as floor joists.
In conventional construction practice, solid wood members, such as 2 .times. 10 lumber, have been commonly used for floor joists. In recent years, however, flat floor trusses have been substituted for solid wood floor joists due to the increased cost of solid wood floor joist lumber and the scarcity of long-span lumber of the required dimensions. Flat floor trusses are typically made of less expensive 2 .times. 4 lumber. The wood members comprising the chords of the truss may be of shorter length than the length of the truss because two or more 2 .times. 4 members may be readily spliced together in end-to-end relation. Relatively short lengths of 2 .times. 4 lumber (even scrap lumber from other structures) may be used for the web members of the truss. Thus, flat floor trusses of virtually any desired length (or span) and depth may be fabricated from readily available and inexpensive 2 .times. 4 lumber. Floor trusses are generally lighter in weight than solid wood joist members of comparable strength and may be designed to have a longer span than the span length of commonly available solid wood floor joists. Flat floor trusses can be designed to have a predetermined amount of upward bow or camber so that the truss will be nearly flat when loaded, thus preventing sagging of the floor in the building. Also, flat floor trusses offer considerable labor savings during construction of the building because the electrical wiring, plumbing, heating and air conditioning ducts may be readily routed through openings in the flat floor trusses. Flat floor trusses also provide unobstructed upper and lower faces to which subflooring or ceiling sheathing may readily be nailed.
Flat floor truss fabricating apparatus requires special types of equipment to accomodate the relatively shallow depth of floor trusses and yet must be sufficiently adjustable to support various configurations of wood members at the joints of the truss to be fabricated. Typical prior art flat floor truss fabricating apparatus are shown in U.S. Pat. Nos. 3,388,657, 3,742,569, 3,978,783, and 3,866,350, and in copending U.S. patent application Ser. No. 622,448, filed Oct. 14, 1975, now U.S. Pat. No. 4,024,809.
Because flat floor trusses are only now being introduced into the home construction field, many truss manufacturers are now set up to manufacture only peaked roof trusses which heretofore have been the mainstay of their business. Many truss fabricators, especially smaller, low-volume fabricators, are reluctant to begin making flat floor trusses because of the relatively high capital investment required to purchase special flat floor truss fabricating apparatus or because they may not have sufficient floor space in their existing plants to accommodate an additional truss fabricating machine.